1. Field of the Invention
The present invention concerns a method of manufacturing a sintering product of Fe-Co alloy soft magnetic material.
2. Description of the Prior Art
Fe-Co alloy soft magnetic materials are alloy materials having an order-disorder transformation point and forming a CsCl type ordered lattice phase and, since they show the highest saturation magnetic flux density among alloys known at present, they have been widely used as a magnetic yoke material for pulse motors, printer heads, etc., and vibration plates for headphones.
When the alloy consists only of Fe and Co, the order transformation can not be suppressed by any heat treatment and cold working is impossible. As such it has been necessary to add expensive V or Cr for improving workability. However, even this is not sufficient for completely suppressing the order transformation. Cutting fabrication is necessary for obtaining molding products such as parts, especially. those of complicated shapes, but they are fragile and impossible to be cut because of the presence of the ordered phase and, accordingly, it has been impossible so far to fabricate Fe-Co alloys prepared by melting process into molding products, especially, those having complicated shapes. Furthermore, incorporation of additive elements as described above results in a deterioration of the soft magnetic property.
For overcoming such a drawback, although there has been attempted to produce them by using powder metallurgy, this still involves a problem. For instance, Japanese Patent Laid Open Sho No. 62-63617 discloses a method of mixing starting powders with a composition of Fe/Co=1 by atom ratio, admixing a lubricant to prepare a dust core, removing the lubricant, applying preliminary sintering at 750.degree.-850.degree. C. in hydrogen, applying compression molding again, applying sintering in hydrogen at 1300.degree.-1400.degree. C., maintaining the product in a hydrogen atmosphere at 800.degree.-900.degree. C. and then applying oil quenching.
The thus-obtained sintering product has improved magnetic characteristics when applying heat treatment (cooling applied by quenching) as compared with leaving the product as sintered, but the magnetic flux density and the maximum magnetic permeability are poor as compared with the magnetic characteristics of products prepared by a melting process and they are not yet satisfactory for practical use.